A moving company is called into a building and asked to relocate 520 bricks to a location 15 meters above the ground. If each brick is 4 kilograms, what amount of work will be needed to accomplish the task? A. 229,320 J B. 305,760 J C. 588,000 J D. 203,840 J
The Correct Answer and Explanation is:
gravity: Work=Force×Distance\text{Work} = \text{Force} \times \text{Distance}Work=Force×Distance
Since the work is done to lift the bricks vertically, the force required is equal to the weight of the bricks (mass × gravity). Here’s how we compute it:
Step-by-step solution:
- Number of bricks = 520
- Mass of each brick = 4 kg
- Total mass = 520 × 4 = 2080 kg
- Distance = 15 meters
- Acceleration due to gravity (g) ≈ 9.8 m/s²
Now calculate the total weight (force): Force=Mass×g=2080×9.8=20,384 N\text{Force} = \text{Mass} \times g = 2080 \times 9.8 = 20,384 \, \text{N}Force=Mass×g=2080×9.8=20,384N
Now calculate the work: Work=Force×Distance=20,384×15=305,760 Joules\text{Work} = \text{Force} \times \text{Distance} = 20,384 \times 15 = 305,760 \, \text{Joules}Work=Force×Distance=20,384×15=305,760Joules
✅ Correct answer: B. 305,760 J
Explanation
In physics, work is defined as the energy transferred when a force is applied over a distance. In this problem, the force comes from lifting the bricks upward against the pull of gravity. The work done by the moving company is equal to the total energy required to lift all the bricks to the desired height.
Each of the 520 bricks weighs 4 kilograms, giving a total mass of 2080 kilograms. Since the bricks are being lifted vertically, the force needed to lift them is equal to their weight, which is mass multiplied by the acceleration due to gravity (9.8 m/s²). This results in a total force of 20,384 newtons.
The bricks are lifted 15 meters above the ground, so the work done is this force multiplied by the vertical distance. Multiplying 20,384 newtons by 15 meters gives a total work of 305,760 joules.
It’s important to note that this calculation assumes the lifting is done slowly and steadily, without any acceleration or friction losses. In real-world scenarios, extra work may be needed due to inefficiencies, but in pure physics terms, this is the ideal amount of energy required.
Thus, the correct and scientifically accurate answer is 305,760 joules, or option B.
